Dialysis to support a patient whose renal function has decreased to the point where the kidneys can no longer sufficiently function is well known. Generally, two principal dialysis methods are utilized: hemodialysis; and peritoneal dialysis.
In hemodialysis, the patient's blood is passed through an artificial kidney dialysis machine. A membrane in the machine acts as an artificial kidney for cleansing the blood. Because the treatment is extracorporeal, it requires special machinery and generally, a visit to a center or hospital that performs the treatment.
Peritoneal dialysis (hereafter “PD”) was developed to provide an alternative therapy to hemodialysis. PD utilizes the patient's own peritoneum (a membranous lining of the abdominal cavity) as a semi-permeable membrane. With its good perfusion, the peritoneum is capable of acting as a natural semi-permeable membrane.
PD periodically infuses sterile aqueous solution into the peritoneal cavity. This aqueous solution is called PD solution or dialysate. Diffusion and osmosis exchanges take place between the solution and the blood stream across the peritoneum. These exchanges remove the waste products that the kidneys normally excrete. The waste products typically consist of solutes like urea and creatinine. The kidneys also function to maintain proper levels of other substances, such as sodium and water, which also need to be regulated by dialysis. The diffusion of water and solutes across the peritoneal membrane during dialysis is called ultrafiltration.
In continuous ambulatory PD, a dialysis solution is introduced into the peritoneal cavity utilizing a catheter, normally placed by a doctor. An exchange of solutes between the dialysate and the blood is achieved by diffusion.
Certain PD machines are automated. These machines are called cyclers. Cyclers are generally designed to automatically infuse, dwell, and drain PD solution to and from the patient's peritoneal cavity. A cycler is particularly attractive to a PD patient because it can be used at night while the patient is asleep. This frees the patient from the day-to-day demands of continuous ambulatory PD during his/her waking and working hours.
The treatment typically lasts for several hours. It often begins with an initial drain cycle to empty the peritoneal cavity of spent dialysate. The sequence then proceeds through a succession of fill, dwell, and drain phases that follow one after the other. Each phase is called a cycle.
Unlike hemodialysis machines, which are typically operated by doctors or trained technicians, PD machines may be operated by the patient. Many PD patients travel which require those patients to take their PD apparatus with them in a car, train, or plane.